Existing concrete distributing apparatuses generate pressure fluctuations when they pump concrete; especially, since these pumping apparatuses usually employ a double-cylinder pumping mode, the pressure fluctuations are more severe at the moment of the two cylinders alternative working. The transfer pipeline and boom will be subject to severe shocks regardless of the pumping mode; therefore, the boom will have vibrations and the end hose will whip; such a phenomenon will not only have adverse effect to the operation of the entire apparatus but also shorten the service life of the boom and even cause accidents.
As for existing boom vibration suppression techniques for concrete distributing apparatuses, for example, in an existing boom vibration suppression method, the information on oil pressure in a boom oil cylinder and/or vibration suppression cylinder is detected, the acquired oil pressure information is sent to a control unit of the vibration suppression cylinder, and the control unit of the vibration suppression cylinder analyzes and processes the information and outputs a control signal. The capacity of a rod cavity and the capacity of a rod-less cavity in the vibration suppression cylinder are controlled and regulated according to the control signal, so that the vibration suppression cylinder produces pulse vibrations, which result in vibrations on the end of the boom, the amplitude of which is smaller than or equal to the amplitude of vibrations on the end of the boom incurred by pumping operation and the phase of which opposite to the phase of vibrations on the end of the boom incurred by pumping operation.
In another existing boom vibration suppression method, the vibrations on the end of the boom and the posture of the boom are detected, the acquired signals are transmitted to a vibration suppression control unit, the vibration suppression control unit analyzes and processes the signal and outputs a control signal to control the piston's position in the boom oil cylinder (i.e., capacity of a rod cavity and capacity of a rod-less cavity in the boom oil cylinder), so that the internal force in the boom produces vibrations having phase opposite to that of original vibrations on the end of the boom.
Though the above-mentioned two existing methods in the prior art employs different control signal acquisition approaches and detect different variables, both of them produce vibrations having phase opposite to that of original vibrations on the end of the boom by changing the capacity of a rod cavity and the capacity of a rod-less cavity in the boom oil cylinder and thereby suppress the original vibrations of the boom. Since such control methods introduce pulse vibrations in opposite phase, they will inevitably increase the stress in the boom system and have adverse effect to the service life of the boom. In addition, in the first method in the prior art, since only a few of variables are detected, the control signal obtained with insufficient information is difficult to adapt to booms in different postures; in other words, the control signal is often applicable to booms in a specific posture only; in case the posture of the boom varies, it will be difficult to obtain a satisfactory control effect with the obtained control signal. The second method in the prior art detects the vibrations on the end of the boom and the posture of the boom directly, and the control signal obtained in that way reflects relatively comprehensive information; however, the algorithm for obtaining the control signal is complex, and the robustness of control is poor because there are too many parameters to consider.